Piezoelectric ceramic composition



Mardi 17,1970 Ts'uNEoAKAsl-n ETAL 3,501,407

PIEZOELECTRIG CERAMIC COMPOSITION y March 17, 1970 Original Filed Oct.17, 1966 rsuNrl-:o AKAsHl ETAL.

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March 17, 1970 rsUNEo AKAsHl ETAL 5 Sheets-Sheet 5 1 N VEN TORS AKASH/M4540 7a4/MHA sm ,vak/o rsusoa/CH/ /MQ @wf/"M TTOR/VEYS 3,501,407PIEZOELECTRIC CERAMIC COMPOSITION Tsuneo Akashi, Masao Takahashi, andNorio Tsubouchi, Tokyo, Japan, assignors to Nippon Electric Company,Limited, Tokyo, Japan, a corporation of Japan Original application Oct.17, 1966, Ser. No. 587,241. and this application Apr. 16, 1969, Ser. No.

9 Int. Cl. C04b 35/00; H01v 7 /02; H03h 9/00 U.S. Cl. 252-62.9 4 ClaimsABSTRACT OF THE DISCLOSURE A piezoelectric ceramic composition of theformula (PbuAv)(ZrxTiySnz)O3, where A represents at least one memberselected from a group consisting of calcium, strontium, and barium andu, v, x, y and z are given by: u=0.75-l.00, v=0.00-0.25, u{-v=1.00,x=0.00-0.90, y=0.100.60, z=0.00-0.65, and x-l-y-i-z=l.00, contains a setof additional constituents consisting of a manganese compound equivalentin amount to a maganous oxide of from 0.02 to 1.0 weight percent and anickel compound equivalent in amount to a nickel oxide of from 0.02 to2.0 weight percent, each of the weight percentages being the percentageof the total weight of said ceramic composition.

This is a division of application Ser. No. 587,241 filed Oct. 17, 1966.

This invention relates generally to piezoelectric ceramic compositions.More particularly, this invention relates to ceramic compositions Ibasedon a formula of lead zirconate-lead titanate PbZrOa-PbTiOg or a relatedformula lead zirconate-lead titanate lead stannate The present inventionrelates more particularly to lead zirconate-lead titanate-lead stannateceramic compositions which contain, in addition to such compositions,chromium sequioxide (Cr2O3) of from 0.01 weight percent to 0.7 weightpercent of the total weight and also gallium sesquioxide (Ga2O3) of from0.01 weight percent to 1.5 weight percent.

The present invention also relates to ceramic compositions whichcontain, in addition to such compositions, manganous oxide (MnO) of from0.02 weight percent to 1.0 weight percent of the total weight and alsonickel oxide (NiO) of from 0.02 weight percent to 2.0 weight percent.

The present invention further relates to ceramic compositions whichcontain, in addition to such compositions, nickel oxide (NiO) of from0.02 to 2.0 Weight percent and also chromium sesquioxide (Cr2O3) of from0.01 to 0.5 weight percent.

A general object of this invention is to provide ceramic compositionshaving large electromechanical coupling factors and large mechanicalquality factors.

A further object of this invention is to provide piezoelectric materialswhich have both large electromechanical coupling factors and largemechanical quality factors for use as elements of ceramic electric wavefilters and as transducer elements of mechanical filters.

It can be established that a lead zirconate-lead titanate solid solutionPb(`ZrTi)O3, obtained by sintering a mixture of lead zirconate PbZrO3and lead titanate PbTiOa, has piezoelectric properties which are stableagainst United States Patent O ice change of temperature and elapse oftime and that strong piezoelectric activities are achieved in theneighborhood of x=0.520.54 in Pb (ZrX:Ti1 X)O3.

Fundamental measures for evaluating the piezoelectric properties of apiezoelectric material are its electromechanical coupling factor and itsmechanical quality factor. The electromechanical coupling factorrepresents the efficiency of transforming electric oscillation intomechanical vibration and, conversely, of transforming mechanicalvibration into electric oscillation. The mechanical quality factorrepresents the reciprocal proportion of the energy consumed by thematerial during the electrical and mechanical energy interconversion. Alarger mechanical quality factor corresponds to a smaller energyconsumption by the material, and vice versa.

Recently, attention and studies have been directed to ceramic electricwave filters wherein use is made of piezoelectric cerarnics as theelement or elements of the filters, and to mechanical filters whereinuse is also made of piezoelectric ceramics as the transducer ortransducers thereof. The qualities desired for the piezoelectricceramics used in these fields of application are as follows: For theelements of ceramic electric wave filters, the electromechanicalcoupling factor must have a desired value selected from a range betweenan extremely large value and a very small value, and the mechanicalquality factor should have as great a value as possible. For thetransducer elements of mechanical filters, both the electromechanicalcoupling factor and the mechanical quality factor must -be as large aspossible. Thus, the properties required for the transducer elements ofmechanical filters are consistent with that particular set of propertiesdemanded for the elements of ceramic electric wave filters in which theelectromechanical coupling factor is large.

The electromechanical coupling factor determines the frequency spacingbetween the attenuation poles of the filter in such a manner that agreater electromechanical coupling factor produces a filter of widerfrequency Spacing and a smaller electromechanical coupling factorresults in a filter of narrower frequency spacing. In other words, theelectromechanical coupling factor of the piezoelectric material for theelements of'ceramic filter must be selected in compliance with thefrequency spacing between the attenuation poles of the particular filterin which the material is to be used and that factor must therefore beavailable or adjustable between an extremely small value and a verylarge value according to the characteristics of the filter. Themechanical quality factor also determines the loss in the pass band andthe loss at the attenuation poles of the filter. The values desired fora filter therefore determine the lowest allowable limit of the.mechanical quality factor of the piezoelectric material to be used inthe filter. In other words, a piezoelectric material having a smallermechanical quality factor than required can not provide a satisfactoryfilter, while a piezoelectric material having a greater mechanicalquality factor than required can easily provide a filter of excellentcharacteristics. A greater mechanical quality factor is generallynecessary for piezoelectric materials to be used in a filter of narrowerpass band or for a case where a smaller electromechanical couplingfactor is required.

As has so far been described, piezoelectric material for use in filtersmust be furnished with the electromechanical coupling factor selectedfrom a wide range according to the characteristics and the fields ofapplication of the particular filter and with the largest possiblemechanical quality factor.

According to this invention, the basic composition of leadzirconate-lead titanate may incorporate any one of the respective pairsof additives above noted, that is, Ga203 and Cr2O3, NiO and MnO, and NiOand Cr203, in the required amounts and, in such basic composition,

at least one member of the group consisting of barium (Ba), strontium(Sr) and calcium (Ca) may replace up to atom percent of the lead (Pb)contained in the basic composition.

It is especially noted, as will be explained by way of example, thatimprovements in the characteristics of the various compositions of thisinvention may be brought about by the addition of gallium oxide,chromium sesquioxide, nickel oxide, and manganous oxide, in the amountsand in the combinations specied herein, and such improvements clearlyresult from the presence of gallium ions, chromium ions, nickel ions andmanganous .or manganese ions, respectively, in the lead zirconate-leadtitanate ceramics. Gallium compounds [for example, GaCl3 or Ga2(SO4)3],other than gallium sesquioxide (Ga203), may be used in the compositionso as to provide an amount of gallium ions equivalent to that derivedfrom gallium sesquioxide (Ga-203). Similarly chromium compounds (forexample CrCla), other than chromium sesquioxide (Cr203), may be used inthecomposition so as to provide an amount of chromium ions equal to theamount of chromium ions provided by chromium sesquioxide (Cr203) when itis used in the composition. Also, if nickel compounds, other than NiO,are employed, they should be supplied in amounts to yield nickel ions inan amount equivalent to that of NiO. Furthermore, if manganous ormanganese compounds, other than MnO, are utilized, they should be usedin amounts equivalent to the desired weight of MnOl for yielding theappropriate amount of manganous or manganese ions.

This invention may also expressed as residing in a piezoelectric ceramiccomposition whose basic composition may be represented by Pb(ZrXTiySnZ)O3, where x, y, and z represent a set of mol ratios and suchmol ratios are given by Compositions outside of the suggested ranges arenot practically operable because of their seriously reducedelectromechanical coupling factors. The largest electromechanicalcoupling factor is obtainable in cases in which x, y, and z are in thevicinities of 0.52-0.53, 0.480.47, and 0.00, respectively. Also,excellent piezoelectric properties are obtained even if at least onemember of the group of calcium, strontium and barium may be substitutedfor up to 25 atom percent of the lead contained in the basiccomposition.

Details of certain earlier types of replacements or substitutions inpiezoelectric materials are generally described, for example, in Journalof the National Bureau of Standards, 55 (1955), 239 by B. Jaffe, R. S.Roth, and S. Marzullo and in U.S. Patents No. 2,906,710 issued to F.Kulcsar et al., on Sept. 29, 1959, and No. 3,068,177 issued to I. A.Sugden on Dec. 11, 1962.

Said basic composition may contain, as additional constituents, bothgallium sesquioxide (Ga203) of from 0.01 weight percent to 1.5 weightpercent of the total weight and chromium sesquioxide (Cr-03) of from0.01 weight percent to 0.70 weight percent of the total weight.

The compositions of this invention may also consist of the above-notedbasic composition of P1b(ZrXTiySnZ)O3 where x, y, and z are given by theabove equations and where at least one member of the group of calcium,strontium and barium may be replaced by up to 25 atom percent of lead(Pb) contained in the basic composition, and such basic composition mayinclude additional constituents of nickel oxide (NiO) of from 0.02weight percent to 2.0 Weight percent and also manganese oxide (MnO) offrom 0.02 weight percent to 1.0 weight percent.

The compositions of this invention may also consist of the above-notedbasic composition of Pb (ZrXTiySnz) O3, where x, y, and z are given bythe above equations and where at least one member of the group ofcalcium, strontium and Ibarium may be replaced by up to 25 atom percentof the lead (Pb) contained in said basic composition, and to said basiccomposition there may be added constituents of nickel oxide (NiO) offrom 0.02 weight percent to 2.0 weight percent and also chromiumsesquioxide (Cr203) of from 0.01 weight percent to 0.5 weight percent.

The resulting basic compositions above-noted are especially suitable aspiezoelectric materials for the elements of electric wave filters andfor the transducer elements of mechanical filters.

As for the piezoelectric materials to be used in the elements of ceramicelectric wave lters, it is necessary that such materials provide anelectromechanical coupling factor with an optimum value selected from aWide range extending from an extremely large value to a very smallvalue, and it is also desirable for the mechanical quality factor tohave as great a value as possible. This criterion is described, forexample, in Electronic Engineering, vol. 33 (1961), No. 3, pp. 171-177,by R. C. V. Macario, entitled Design Data for Band-Pass Ladder FiltersEmploying Ceramic Resonators.

This invention will be better understood from the more detaileddescription hereinafter following when read in connection with theaccompanying drawing in` which:

FIG. 1 shows curves representing the electromechanical coupling factorKr for the radial mode vibration and the mechanical quality factor Qm,both plotted as ordinates, against abscissae representing the content ofchromium sesquioxide (Cr2O3) in ceramics obtained by adding, to thecomposition Pb(Zr0 52Ti0-43)O3, the compound gallium sesquioxide (Ga203)of 0.50 Weight percent and the compound chromium sesquioxide (Cr203) ofup to 0.70 weight percent. These curves are based upon cornpositionsgiven, for example, in Table 1 listed hereinafter.

FIG. 2 shows curves representing the factors Kr and and Qm, lbothplotted as ordinates, against abscissae representing the content ofgallium sesquioxide (Ga203) in ceramics obtained by adding, to thecomposition Pb (Zr0,52Ti0.48)O3, the compound chromium sesquioxide(Cr203) of 0.10 weight percent and the compound gallium sesquioxide(Ga203) of up to 1.5 Weight percent. The curves of FIG. 2 are based oncompositions given, for example, in Table 2 listed hereinafter.

FIGS. 3 and 4 show similar curves representing the electromechanicalcoupling factor Kr for the radial mode vibration and the mechanicalquality factor Qm, lboth plotted as ordinates, for the composition towhich NiO and MnO compounds have been added. In FIG. 3, the abscissaeare MnO and in FIG. 4 they are NiO. The curves of FIG. 3 are based oncompositions given in Table 5; the curves of FIG. 4 are based on Table6.

FIGS. 5 and 6 show similar curves for the same Kr and Qm factors. Theabscissae of FIG. 5 are related to the addition of the compound chromiumsesquioixde (Cr203), while the abscissae of FIG. 6 are related to theaddition of the compound nickel oxide (NiO). The curves of FIG. 5 arebased on the compositions given in Table 10; the curves of FIG. 6 arebased on the compositions of Table 11.

Reference is now made to FIG. 1 showing curves representing, as alreadynoted, the -electromechanical coupling factor Kr for the `radial modevibration and the mechanical quality factor Qm, both plotted asordinates as shown, against abscissae representing the content ofchromium sesquioxide (Cr203) in ceramics whose basic composition isgiven by the term Pb (Zro'zTiMQOg and whose additional constituents aregallium sesquioxide (GazOg) of 0.50 weight percent of the total weightand chromium sesquioxide (Cr203) of up to 0.70 weight percent of thetotal weight. This composition and the additives which arel consideredin Table 1, provide the basis for the curves of FIG. 1.

The lead zirconate-lead titanate composition given by the term Pb(Zr52Ti0.48)O3, if piezoelectrically activated through polarizationtreatment effected at 100 C. has a set of values of about 42 percent forthe factor Kr and about 250 for the factor Qm. FIG. 1 and Table 1 showthat the addition of 0.50 weight percent of gallium sesquioxide (Ga203)alone to the composition augments the factor Qns to a remarkable extent.The curves and Table 1 furthermore show that the addition of bothgallium sesquioxide (Ga203) of 0.50 weight percent and chromiumsesquioxide (Cr203) of from 0.01 weight percent to 0.70 weight percentremarkably augments the lvalue of the factor Kr while not deterioratingor even further augmenting the value of the factor Qm resulting from theaddition of gallium sesquioxide (Ga203) alone. This combination providesexcellent piezoelectric materials for use in ceramic electric filterswhere a large Kr factor is required and for use in transducers ofmechanical iilters. The curves still further show that the piezoelectricactivities are little improved by coexistence of chromium sesquioxide(Cr203) and lgallium sesquioxide (Ga203) in case the content of chromiumsesquioxide V(Cr2O3) is less than 0.01 weight percent. Although notshown by the curves, the results of experiments also show that chromiumsesquioxide (CrgOa), if contained in excess of 0.70 weight percent,reduces the electric resistivity of the composition so as to disablethorough polarization treatment and this results in a decrease in bothof the Kr and Qm factors and a consequent marked deterioration of thepiezoelectric properties.

In view of the above results, the effective range for the content ofchromium sesquioxide (Cr2O3) in the case in which both galliumsequioxide (Ga203) and chromium sesquioxide (Cr2O3) are added to thecomposition, is set at between 0.01 weight percent and 0.70 weightpercent.

Reference is now made to FIG. 2 which shows curves which represent, asalready noted, the relations between factors Kr and Qm, on the one hand,and the content of gallium sequioxide (Ga2O3 on the other hand, in theceramics whose basic composition is lead zirconate-lead titanate givenby the formula Pb(Zr0.52Ti0-48)O3 as was the case with FIG. l and whoseadditional constituents are gallium sesquioxide (Ga203) of up to 1.5weight percent and chromium sesquioxide (Cr2O3) of 0.10 weight percent.The combination of such constituents is included in Table 2.

FIG. 2 and Table 2 show that the addition of 0.10 weight percent ofchromium sesquioxide (Cr202) alone raises the value of the Kr and Qmfactors as compared with the Kr and Qm factors of lead zirconate-leadtitanate represented by the composition Pb(Zr0,52Ti 48)O3. The curves ofFIG. 2 when considered with Table 2 further show that the addition ofchromium sesquioxide (Cr-203) of 0.10 weight percent and galliumsesquioxide (Ga2O3) of from 0.01 weight percent to 1.5 weight percentnot only further augments, or, at the worst, only slightly deteriorates,the value of the factor Qm resulting from the addition of chromiumsesquioxide (Cr2O3) but also remarkably raises the value of the factorKr to provide materials having excellent piezoelectric properties. Thecurves still further show that the piezoelectric properties are littleimproved even by coexistence of the compounds lgallium sesquioxide(Ga2O3) and chromium sesquioxide (Cr2O3) in case the content of galliumsesquioxide (Ga203) is less than 0.01 weight percent. Although not shownby the curves, the results of experiments show that improvements in theproperties are scarcely expected from the addition of both galliumsequioxide (Ga203) and chromium sequioxide (Cr203) if the content ofgallium sesquioxide (Ga203) exceeds 1.5 weight percent. In other words,in case the content of gallium sesquioxide (Ga203) Results shown inTable 1 So that the resulting basic composition may be given byPb(Zr0,52Ti0.48)O3, mol percent of lead monoxide (PbO), 26 mol percentof zirconium dioxide (ZrOg), and 24 mol percent of titanium dioxide(TiO2) were arranged for various mixtures, such constituents weresupplied with an additive of 0.50 weight percent of gallium sesquioxide(Ga2O3), and these constituents were supplied with further additives offrom 0.01 weight percent up to 0.70 weight percent of chromiumsesquioxide (CrzOa). As shown in Table 1, these compounds were thenmixed, respectively, in a ball mill, pre-sintered at 900 C. for an hour,crushed, press-moulded into discs, sintered at 1300 C. for an hour,provided with silver electrodes, respectively, subjected to apolarization treatment at C. for an hour under an electric field of 50kv./ cm., allowed to stand for 24 hours, and then the factors of Kr andQm were measured. The results obtained for the various combinations areshown in Table 1. The results were obtained for the basic compositionalone (No. 1) and for the basic composition with an addition of 0.50weight percent of gallium sesquioxide (Ga203) alone (No. 2).

+0.70 wt. percent CrzOa.

C1 grCl was contained in an amount equivalent. to 0.20 wt. percent ofComparison of the results of Nos. 1 and 2 of Table 1 shows that theaddition of Ga203 of 0.50 weight percent (No. 2) to the basiccomposition (No. l) raises the factor Qm to a large extent. The resultsNos. 3-9 show that the addition of chromium sesquioxide (Cr2O3) inamounts extending from 0.01 weight percent to 0.70 weight percent, withthe content of gallium sesquioxide (Ga203) kept at 0.50 weight percent,remarkably raises the value of the factor Kr while not deteriorating thevalue of Qm for any arrangement including gallium sesquioxide (GazOa).

In the following examples, the results were achieved through treatmentssimilar to those given in the prior example (unless otherwisementioned).

EXAMPLE 2 Results shown in Table 2 Table 2 shows the results obtainedfor a mixture of the composition Pb(Zr0,52Ti0 48)03 and 0.10 weightpercent of the compound chromium sesquioxide (Cr2O3) alone, and formixtures of this same compound Cr203 and compounds of from 0.01 weightpercent to 1.5 weight percent of the compound gallium sesquioxide(Ga203).

TABLE 2 No. Composition (percent) Qm 10 Pb(ZI`0 52To,4a) Orf-0.10 Wt.percent C1703 51 770 11 Pb(ZI`.52Tio,4s) O3+0.01 Wt. percent G3203 54780 +0.10 wt. percent CrzOa.

12 Pb(Zru.52Tiu,4e)O3+0,02 wt. percent GazOs 59 820 +0.10 wt. percentC1103.

13 Pb(Zro.s2Tio.4s)O3+0.05 wt. percent G3203 60 830 +0.10 wt. percentCrQOg.

14 Pb(Z10.52Tiu,4s)O3-l0.l0 Wt. percent G8203 60 830 +0.10 wt. percentCr203.

15 Pb(Zro.s2Tio.4s)O3-I0.20 Wt. percent GazO l 60 S20 +0.10 wt. percentCrzOa.

16 Pb(ZI0,5zTo.45) Ori-1.1 Wt. percent G2203 57 730 +0.10 wt. percentCrzOa.

17 Pb(Zr0.5zTin.4g)O3+1.5 wt. percent GazOg 52 700 +0.10 wt. percentCrz03.

G1 (aCl was contained in an amount equivalent to 0.20 wt. percent of-Comparison of the result No. 1 of Table 1 with the result No. 10 ofTable 2 shows that addition of 0.10 weight percent of Cr2O3 alone to thebasic composition is sufficient to significantly augment both the Kr andQm factors. The results Nos. 11 through 17 show that the addition ofgallium sesquioxide (Ga2O3) of from 0.01 weight percent to 1.5 Weightpercent with the content of chromium sesquioxide (Cr203), kept in allthese cases Nos. l1 to 17 at 0.10 weight percent, remarkably raises thevalue of the factor Kr while further augmenting or, at the worst, onlyslightly reducing, the value of the factor Qm when compared with theresults of the addition of chromium sesquioxide (Cr2O3) (see Table 1).These results show that these compounds yield excellent piezoelectricmaterials for use in cases where a large Kr factor is specificallyrequired.

EXAMPLE 3 Results shown in Table 3 Table 3 shows the Kr and Qm factorsobtained from lead zirconate-lead titanate compositions wherein 0.45,0.50, and 0.55 were selected for x in the compositional form-ulaPb(ZrXTi1 X)O3 and from compositions obtained by having both the 0.50weight percent of gallium sesquioxide (Ga203) and the 0.10 weightpercent of chromium sesquioxide (C12O3) contained in each of the basiccompositions.

+0.10 wt. percent Cr203.

These results clearly show that, regardless of change of the contents ofZr and Ti in the basic composition in the manner exemplified in thisTable 3, the piezoelectric Results shown in Table 4 Table 4 shows the Krand Qm factors obtained when both a compound of 0.50 weight percent ofgallium Sesquioxide (621203) and a compound of 0.10 weight percent ofchromium sesquioxide (Cr2O3) are contained in each of lead titanate-leadzirconates, wherein the ZraTi ratio is 52:48, and wherein barium (Ba)and strontium (Sr) are substituted for 5.0 atom percent of the leadforming a portion of the basic compositions, respectively.

TABLE 4 Kr No. Composition (percent) Qm 24(PbosBaus)(Zro,szTiu.4s)Os+0.50 Wt. per- 61 660 cent Ga203+0.10 wt.percent CrzOa. 25 (Pbosssluns)(ZI`0.52Tio.4a)O3-|0.50 Wt. pel- 58 670cent Ga203+0.10 Wt. percent CrQOa.

Results shown in Table 5 So that the resulting basic composition may berepresented by the formula Pb(Zr0.54Ti0-48)O3, the composition includedpowder consisting of 50` mol percent of lead monoxide (PbO), 26 molpercent of zirconium dioxide (Zr02), and 24 mol percent of titaniumdioxide (TiO2), and to this composition were added both a 0.20 weightpercent of nickel oxide (NiO), and a compound of manganous oxide (MnO),in the stated amounts specied in Table 5, but in two of the cases (Nos.7 and 9) a compound of manganese carbonate (MnCO3) in the amounts notedin Table 5 was used as an additional constituent (the MnCO3 beingcomputed as if MnO were added). These chemicals were mixed in a ballmill. Mixed powder of the respective kinds was pre-sintered at 900 C.for an hour, crushed, press-moulded into discs, and sintered at 1300 C.for an hour. The resulting ceramic discs were provided with silverelectrodes and piezoelectrically activated through polarizationtreatment at C. for an hour under an electric eld of 50 kv./cm. Afterthe discs had been allowed to stand for 24 hours, the electromechanicalcoupling factor Kr for the radial mode vibration and the mechanicalquality factor Qm were measured to evaluate the relative piezoelectricactivities. Typical results are shown in Table 5.

TABLE 5 No. Composition (percent) Qrn Pb(Z1'|J 5zTO.4a) O3- 42 250Pb(Zr0.52Tio 4s)03+0.20 wt. percent NiO 50 270 +0.02 Wt. percent MnO.

4 Pb(Zro.52Ti0.4s)Oa+0.20 wt. percent NiO 66 270 +0.05 wt. percent MnO.

5 Pb(Zro.52Ti0 4s)O3+0.20 wt. percent NiO 66 330 +0.10 wt. percent MnO.

6 Pb(Zr0,51Ti0.4g)O3+0.20 wt. percent NiO 65 940 +0.20 Wt. percent MnO.

Pb(Zr.s2Tio.4s)Oa+0.20 wt. percent NiO 63 980 +0.30 wt. percent MnO.1

8 Pb(Zru.5zTio,4s)Oa-i0.20 wt. percent NiO 60 840 +0.50 wt. percent MnO.

9 Pb(Zro.52Ti0,4s)O.-,+0.20 wt. percent NiO 58 630 0.70 wt. percentMnO.l 10 Pb(Z1o,52Tio,4a)O3-l0.20 Wt. percent NiO 56 380 +1.0 Wt.percent MnO.

l MnOz is added as calculated on the basis of MnO.

Comparison of the results of samples Nos. 1 and 2 of Ta'ble 5 shows thatthe addition of the 0.20 weight percent of nickel oxide (NiO) alone tothe basic composition provides piezoelectric material of raised Kr andQm factors. However, the increase in the value of Qm brought about byaddition of nickel oxide (NiO) alone is not very great. A greaterincrease in the Qm factor and a simultaneous increase in the Kr factorwould therefore provide more improved piezoelectric materials having awider eld of application.

FIG. 3 illustrates curves representing the results of this Example 5.More particularly, the curves show the relations obtained between the Krand Qm factors on the one hand and, on the other hand, the content ofmanganous oxide (MnO) in the case of the composition containing nickeloxide (NiO) of 0.20 weight percent and also manganous oxide (MnO) of 1.0weight percent r less (in the amount noted, for instance, in Table 5).

As will be clear from Table and FIG. 3, it is possible to raise the Krfactor and remarkably to augment the Qm factor by addition of bothnickel oxide (NiO) and manganous oxide (MnO) to the basic composition.

In general, an increase `of one of the factors Kr and Qm reduces theother factor. On the contrary, however, the addition of both nickeloxide (NiO) and manganous oxide (MnO) to the basic composition makes itpossible to simutaneously raise both factors Kr and Qm remarkably and toobtain piezoelectric materials having both factors Kr and Qmsignificantly increased. This serves to provide excellent material foruse in the piezoelectric components of ceramic wave filters wherespecically large Kr factors are required and in transducers ofmechanical filters.

In case the content of manganous oxide (MnO) is less than 0.02 weightpercent, coexistence of the compounds nickel oxide (NiO) and manganousoxide (MnO) hardly improves the piezoelectric activities achieved by thepresence of nickel oxide (NiO) alone. In case the content of manganousoxide (MnO) exceeds the 1.0 weight percent limit, the properties are somuch and so rigidly altered regardless of presence of nickel oxide (NiO)that the coexistence of nickel oxide (NiO) scarcely improves theactivities.

In view of the above, a range between `0.02 weight percent and 1.0weight percent has been selected for the effective range of themanganous roxide (MnO) content.

EXAMPLE 6 Results shown in Table 6 Table 6 shows the results obtainedfor a mixture of the basic composition of Pb(Zr052Ti(.1)O3 that is thesame as in Example 5 supra and an additional constituent of 0.20 weightpercent of manganous oxide (MnO) alone (case No. 11) and for mixtureswith further additions of nickel oxide (NiO) of from 0.02 weight percentto 2,0 weight percent as indicated in Table 6 for cases Nos. 12 to 17.

+0.20 wt. percent MnO.

1 NiCO3.2Ni(OH)2.4I-I2O may be added as calculated on the basis ofnickel oxide (NiO).

`Comparison of the result of Case No. l of Example 5 shown in Table 5with the result of Case No. ll of Table 6 shows that addition of 0.20weight percent of manganous oxide (MnO) alone to the basic compositionprovides a piezoelectric material having fairly augmented Kr and Qmfactors. It should be understood, however, that further increases infactor Kr and further increases in factor Qm, which are alreadyaugmented by addition of manganous oxide (MnO) alone, would providepiezoelectric materials having a wider eld of application because theyare improved piezoelectric materials.

Referring to FIG. 4, curves are shown to represent the results of thisExample 6. More particularly, these curves show the relation betweenfactors Kr and Qm on the one hand and, on the other hand, the content ofnickel oxide (NiO) in cases in which both nickel oxide (NiO) of 2.0weight percent or less and manganous oxide (MnO) of 0.20 weight percent(unchanged in amount) are added to the basic composition Pb(Zr0,52Ti048)O8, as is exemplified in Table 6.

As is clearly shown in Table 6 and FIG. 4, it is possible to providepiezoelectric materials having remarkably raised Kr land Qm factors byaddition of both nickel oxide (NiO) and manganous oxide (MnO). ,A

In case the content of nickel oxide (NiO) is less than 0.02 weightpercent, coexistence of nickel oxide (NiO) and manganous oxide (MnO)contributes but little to the improvement of the piezoelectricproperties attained by presence of manganous oxide (MnO) alone. In casethe content of nickel oxide (NiO) exceeds 2.0 weight percent, theproperties are so much and so rigidly altered regardless of presence ofmanganous oxide (MnO) that the coexistence of manganous oxide (MnO)hardly improves the properties.

In view of the above, a range between 0.02 weight percent and 2.0 weightpercent is selected for the effective range of the nickel oxide (NiO)content.

It should be noted here that the improvements made in the piezoelectricproperties by addition of both nickel oxide (NiO) and manganous oxide(MnO) clearly result from the presence of nickel and manganous ions. Itis therefore possible, by introducing nickel ions into the solution, touse, besides nickel oxide (NiO), nickel carbonate [Ni'CO32Ni(OH)2-4H2O]or any other nickel compound which is easily thermally decomposed intonickel oxide (NiO). Likewise, manganous ions may be put into thesolution by using MnCO3, manganese dioxide (MnOg), or any othermanganese compound which is easily converted at higher temperatures intoMnO. In case nickel compounds other than nickel oxide are utilized, theyshould be used in an amount equivalent to the desired weight of nickeloxide (NiO). Itis likewise true that manganese compounds other thanmanganous oxide (MnO); if utilized, should be used in an amountequivalent as calculated on the basis of the presence of manganous oxide(MnO). Use of such compoundsis exemplified by the compositions Nos. 7and 9 of Table 5 and No. 15 of Table 6. In this connection, it should beunderstood that nickel oxide (NiO) and manganous oxide (MnO) as usedhereafter may also mean such nickel and manganese compounds which maydecompose at raised temperatures into nickel oxide (NiO) and manganousoxide (MnO) respectively.

EXAMPLE 7 Results shown in Table 7 Table 7 shows typical piezoelectricKr and Qm properties of ceramics produced by selecting values of 0.00for z, 0.50-055 for x, and O.50-0.45 for y, in the compositionPb(ZrxTiySnz)O3 and by adding thereto both a 0.20 weight percent ofnickel oxide (NiO) and a 0.20 weight percent of manganous oxide (MnO).

+0.20 Wt. percent MnO.

Table 7 clearly shows that the indicated changes in the above-notedvalues of x and y in the ceramic composition (which obviously does notinclude tin Sn) and are given by Pb(ZrXTiy)O3, do not deteriorate thepiezoelectric properties. The employment of nickel oxide (NiO) andmanganous oxide (MnO) in the modified composition serve to maintain theKr and Qm factors relatively high in values.

Recapitulating, the compositions improved through addition of bothnickel oxide (NiO) and manganous oxide (MnO) have excellentpiezoelectric properties for use in manufacturing ceramic wave filtersand transducers for mechanical lters.

EXAMPLE 8 Results shown in Table 8 Table 8 shows the piezoelectricproperties of ceramics given by the formula Pb(ZrXTiySnZ)O3, Where 0.47,0.48, and 0.05 are selected for x, y, and z, respectively, in oneexample (No. 24) and Where 0.42, 0.48, and 0.10 are selected for x, y,and z, respectively, in another example (No. 26) and of the ceramicsobtained by adding, to each of these examples, 0.20 weight percent ofnickel oxide (NiO) and 0.20 Weight percent of manganous oxide (MnO)(Nos. 25 and 27, respectively).

Comparison of the results of Nos. 4 and 6 of Table 5 with the results ofTable 8 makes it clear that substitution of Sn for a portion of Pb(ZrTi)O3 does not degrade piezoelectric properties which were improvedby addition of both nickel oxide (NiO) and manganous oxide (MnO). Inother words, substantially equal improvements in piezoelectricproperties are expected by the addition of both nickel oxide (NiO) andmanganous oxide (MnO) from the composition Pb(Zr-Ti-Sn)03 as from thecomposition Pb(Zr-Ti)O3.

TABLE 8 Kr No. Compositlon (percent) Qm 24 Pb (ZroArTioAsSIlons) 03 40200 25 Pb(Zru.41T1n 4gSn005) Ori-0.20 wt. percent 63 910 NiCd-0.20 Wt.percentMnO. 26 Pl) (ZI'04zTin,4gSI10,m) O3 41 300 27Pb(Zro.42Tlo,4gSIlo.io)Orl-0.20 Wt. percent 62 930 NiO-I-0.20 wt.percentMnO.

EXAMPLE 9 Results shown in Table 9 In case at least one member of thegroup of calcium, strontium and barium is substituted for atom percentof Pb in the composition No. 27 shown in Table 8, then the results shownin Table 9 are obtained.

percent Ni0+0.20 wt. percent MnO.

Table 9 clearly demonstrates that piezoelectric properties are equallyWell improved by the coexistence of nickel oxide (NiO) and manganousoxide (MnO) for the cases where at least one member of the group ofcalcium, strontium and barium is substituted for a portion of the basiccomposition (as in Table 9) and the cases Where no such substitution iseffected in such basic composition (as in No. 27, for example, of Table8).

It should be noted again that the piezoelectric ceramic composition,improved as above indicated, cannot be obtained by presence of eitherone of the compounds nickel oxide (NiO) or manganous oxide (MnO) alone;both compounds nickel oxide (NiO) and manganous oxide (MnO) should bepresent. It shouldA further be noted that the piezoelectric propertiesreferred to are obtained after polarization treatment carried out attemperatures (about 50 C.-l50 C.) higher than room temperature. Inasmuchas it is inevitable that polarization-treatment practiced at roomtemperature reduces the value of the factor Kr, such low temperaturepolarization does not comply with the object of this invention.

FIGS. 5 and 6 show curves for the electromechanical coupling factor Krand the mechanical qualityfactor Qm for basic compositions in whichnickel oxide (NiO) and chromium sesquioxide (Cr203) are the additives.

EXAMPLE 10 Results shown in Table 10 The basic composition used in thisexample may be represented by the term Pb(Zr0 52Ti0 48)O3, in whichthere are combined a powder consisting of 50 mol percent of leadmonoxide (PbO), 26 mol percent of zirconium dioxide (ZrOz), and 24 molpercent of titanium dioxide (TiOg), with 0.50 weight percent of nickeloxide (NiO) provided as an additional constituent, and With a furtheraddition of chromium sesquioxide (Cr203) of from 0.01 weight percent to0.50 Weight percent. These were mixed in a ball mill, pre-sintered at900 C. for an hour, crushed, press-moulded into discs, and sintered at1300 C. for an hour. The resulting ceramic discs were provided withsilver electrodes and piezoelectrically activated at 100 C.

for an hour under an electric eld of 50 kv./cm. After the discs havebeen allowed to stand for 24 hours, the electromechanical couplingfactor Kr for the radial mode vibration and the mechanical qualityfactor Qm were measured to evaluate the piezoelectric activities.Typical results obtained are shown in the following Table l0.

TABLE 10 No. Composition (percent) Qm 1 Pb(ZI'o 52Tio,45) Os 42 250 3Pb(Zro.szTiu.4a)Ori-0.50 wt. percent NiO-I- 60 290 0.01 wt. percentCrzOg.

4 Pb(Zro.52Tio.4a)O3-|0.50 wt. percent NiO-I- 64 380 0.02 wt. percentCrzOg.

5 Pb(Zro.52Tio.4)0ai-O.50 Wt. percent N10-l- 68 590 0.05 wt. percentCrzOa.

6 Pb(Zro,5zTio,4s)O3+0.50 Wt. percent NiO-I- 66 900 0.10 wt. percentCrzOa.

7 Pb(Zro.52Tio.4s) Ort-0.50 Wt. percent N104- 60 740 0.20 wt. percentCrOaJ 8 Pb(Zro 52150.45) Ori-0.50 wt. percent N10+ 58 620 0.30 wt.percent CrzOaJ 0.50 wt. percent CrzOa.

l Cr2(SO4)3 may be added as calculated on the basis of chromiumsesquioxide (CrzOs).

Comparison of the results Nos. 1 and 2 of Table 10 shows that theaddition of 0.50 weight percent of nickel oxide (NiO) alone to the basiccomposition provides piezoelectric material of raised Kr and Qm factors.However, the value of factor Qm attained by addition of nickel oxide(NiO) alone is still insuiiicient for many purposes. A greater increasein the factor Qm and a concurrent increase in the factor Kr wouldprovide more improved piezoelectric lmaterials having wider fields ofapplication.

FIG. 5 illustrates curves representing the results of Example 10. Moreparticularly, the curves show the relations obtained between factors Krand Qm on the one hand and, on the other hand, the content of chromiumsesquioxide (Cr2O3) in the case in which the composition Pb(Zr0 52Ti048)O3 contains nickel oxide (NiO) of 0.50 Weight percent and alsochromium sesquioxide (Cr203) of 0.05 Weight percent or less.

As will be clear from Ta'ble 10 and FIG. 5, it is possible to raise thefactor Qm substantially and to increase the factor Kr by the addition ofboth nickel oxide (NiO) and chromium sesquioxide (Cr203) to the basiccornposition.

As already noted in other cases, an increase of one of the factors Krand Qm reduces the other factor. But the addition of both compoundsnickel oxide (NiO) and 13 chromium sesquioxide (Cr203) to the basiccomposition simultaneously elevates factors Kr and Qm. This providesexcellent compositions for use as the piezoelectric materials forceramic wave filters where large Kr factors are required and intransducers for mechanical filters.

If the content of chromium sesquioxide (Cr203) is less than 0.01 weightpercent, the coexistence of nickel oxide (NiO) and chromium sesquioxide(Cr2O3) serves little to improve the piezoelectric properties achievedby the presence of nickel oxide (NiO) alone. If the content of chromiumsesquioxide (Cr203) exceeds 0.5 weight percent, the properties are somuch altered regardless of -presence of nickel oxide (NiO) that thecoexistence of nickel oxide (NiO) scarcely improves the properties.

In viewnof the above, a range between 0.01 Weight percent and 0.5 weightpercent is selected for the eifective range of the chromium sesquioxide(Cr203) content for the compositions considered.

EXAMPLE l1 Results shown by Table 1l Table l1 shows the results obtainedfor a mixture of the basic composition of Pb(Zr52Ti0.48)O3 that is thesame as that employed in Example l0, but in this case an additionalconstituent of 0.10 weight percent of chromium sesquioxide (Cr203) alonewas used (No. and there Iwere other cases (Nos. 1l to 16) for mixtureswith additions of nickel oxide (NiO) of from 0.02 weight percent to 2.0weight percent.

0.10 Wt. percent Cr203.

l NiC Oz.2Ni(OH)2.4H2O was added as calculated on the basis of NiO.

Comparison of the result No. 1 of Example 10 with the result No. 10 inTable l1 shows that addition of 0.10 Weight percent of chromiumsesquioxide (Cr203) alone to the basic composition provides apiezoelectric material having fairly elevated Kr and Qm factors. Itshould be understood, however, that further increases in the factor Krand increases in factor Qm, which have already been increased by theaddition of chromium sesquioxide (Cr203) alone, would providepiezoelectric materials having wider fields of application and hencethese would constitute nimproved piezoelectric materials.

In FIG6, curves are shown representing the results of this Example ll.More particularly, these curves show the relation between factors Kr andQm with respect to nickel oxide (NiO) when both nickel oxide (NiO) of2.0 weight percent or less and chroium sesquioxide (Cr2O3) of 0.10weight percent are added to the composition As is clearly shown in Tablell and FIG. 6, it is possible to provide excellent piezoelectricmaterials having substantially ezlevated Kr and Qm factors by theaddition of both nickel oxide (NiO) and chromium sesquioxide (Choa)- Asin other cases, if the content of nickel oxide (NiO) is less than 0.02weight percent, the coexistence of nickel oxide (NiO) and chromiumsesquioxide (Cr203) contributes little to the improvement of thepiezoelectric properties attained by the addition of chromiumsesquioxide (Cr203) alone. If the content of nickel oxide (NiO) exceeds2.0 weight percent, the properties are considerably altered regardlessof presence of chromium sesquioxide (CrzOa). Hence, the coexistence ofchromium sesquioxide (Cr2O3) hardly improves the properties.

In view of the above, a range between 0.02 weight percent and 2.0 weightpercent is selected for the eifective range of the nickel oxide (NiO)content.

The improvements effected in the piezoelectric properties by addition ofboth nickel oxide (NiO) and chromium sesquioxide (Cr2O3) clearly resultfrom presence of nickel and chromium ions. As in other cases, the ioncontent is the significant item. It is therefore possible, byintroducing nickel ions into the mixture, to use, in substitution fornickel oxide (NiO), the compound nickel carbonate [NiCO32Ni(OH)2-4H2O]or any other nickel compound which is easily thermally decomposed intonickel oxide (NiO). Likewise, chromium ions may be put into thecomposition by using, instead of chromium sesquioxide (Cr203), thecompound chromium sulphate [Cr2(SO4)3] or any other chromium compoundwhich is easily thermally decomposed into chromium sesquioxide (Cr203).In case nickel and/or chromium compounds other than nickel oxide (NiO)and chromium sesquioxide (Cr203) are utilized, they should be used inamounts equivalent to their respective desired weights of nickel oxide(NiO) and chromium sesquioxide (Cr203). Use of such compounds isexemplified by the compositions Nos. 7 and 8 in Table l0 and No. l5 inTable ll. In this connection, it should be understood that nickel oxide(NiO) and chromium sesquioxide (Cr203), as used in accordance with thisinvention, may also mean or include such nickel and chromium compoundswhich may be decomposed at elevated temperatures into equivalent nickeloxide (NiO) and chromium sesquioxide (Cr203) compounds, respectively.

EXAMPLE 12 Results shown in Table l2 Table l2 shows typicalpiezoelectric properties of the ceramics produced :by selecting andassigning 0.00 for z, U50-0.55 for x and 0.50-0.45 for y in the formulaPb(ZrXTiySnZ)O3 and of the ceramics produced by adding thereto 0.50Weight percent of nickel oxide (NiO) and 0.10 weight percent of chromiumsesquioxide (Cr203). As will be apparent from Table 12, the latteradditives are unchanged in their relative magnitudes in the composition,but the x and y components are varied Within the indicated limits.

TABLE 12 No. Composition (percent) Qm 17 Pb(Z!0 5oTu.5o) O3 29 340 18Pb(Zr0,suTiu .50) Orl-0.50 Wt. percent N1O+ 55 1020 0.10 wt. percentCrzOg. 21 Pb Zl`0 55Tln -45) O3 39 320 22 Pb(Zr0 .55Ti0.45) Orl-0.50 Wt.percent NiO-l- 56 980 0.10 wt. percent CrzOa.

Results shown in Table 13 Table 13 shows the piezoelectric properties ofceramics defined by the formula Pb(ZrXTiySnZ)O3, where 0.47, 0.48, and0.05 are selected for x, y, and z, respectively, of certain compositions(No. 23 of Table 13), and where 15 0.42, 0.48, and 0.10 are selected forx, y, and z, respectively, of certain other compositions (No. 25 ofTable 13), and of the ceramics obtained by adding thereto 0.50 weightpercent of nickel oxide (NiO) and 0.10 weight percent of chromiumsesquioxide (Cr2O3) (Nos. 24 and 26 of Table 13).

TABLE 13 K1' No. Composition (percent) Qm 23 Pb(Zl'u,47Tu.4gSl1o.n5)Oa40 280 24 Pb(ZI0 47Tio 4sS11u o5)O3-l0.50 Wt. percent 65 880 Ni+0.10 wt.percent CrzOa. 25 Pb(Zlo,42Tio,4rSno 1o)O3 41 300 26Pb(Zlo.4zTu.4aSIlnDOH-0.50 Wt. percent 63 870 NiO+0.10 wt. percentCrgOa.

Results shown in Table 14 If at least one member of the group consistingof calcium (Ca), strontium (Sr), and barium (Ba) is substituted for atompercent of lead (Pb) in the composition No. 26 shown in Table 13, thenthe results shown in Table 14 are obtained.

percent NiO+0.10 wt. percent CrzOa.

Table 14 clearly shows that the piezoelectric properties are equallywell improved by the coexistence of nickel oxide (NiO) and chromiumsesquioxide (Cr2O3) in the basic composition No. 26 of Table 13, whereat least one member of the group of calcium (Ca), strontium (Sr), andbarium (Ba) is substituted for a portion of the basic composition No. 26and where no such substitution is effected.

It should be noted again that the piezoelectric ceramic compositionimproved as above can not be obtained by the addition of either nickeloxide (NiO) or chromium sesquioxide (Cr203) alone but only by the jointaddition or coexistence of nickeloxide (NiO) and chromium sesquioxide(Cr203). It is repeated that the improvement in the piezoelectricproperties is obtained through polarization treatment carried out attemperatures (about 50 C.- 150 C.) higher than room temperature.

A considerable number of examples have been offered to establish thenovelty and merit of a modied formula based on the formula expressedgenerally as (PbuAv) (ZrxTiySnz) O3 where A represents one or more ofthe elements calcium, strontium and barium and where 16 The formulation,when modified as noted in the specification, produces outstandingpiezoelectric ceramic materials. The modiiications should include,according to this invention, any pair of the following three pairs ofcompounds: Pair 1:

0.01-1.5 wt. 0.01-0.7 wt. Pair 2:

0.02-0.1 wt. 0.02-2.0 wt. Pair 3:

0.02-2.0 wt. percent NiO 0.01-0.5 wt. percent Cr203 What is claimedis: 1. A piezoelectric ceramic composition having a basic compositionrepresented by the following compositional formula percent Ga203 percentCr203 percent MnO percent NiO where A represents` at least one memberselected from a group consisting of calcium, strontium, and banum and u,v, x, y, and z are given by u: 0.75-1.00 v.=0.00-0.25 w-i-v.: 1.00

x: 0.00-0.90 y: 0.10-0.60 z= 0.00-0.65

characterized in that said ceramic composition contains a set ofadditional constituents consisting of a manganese compound equivalent inamount to a manganous oxide of from 0.02 to 1.0 Weight percent and anickel compound equiv-alent in amount to a nickel oxide of from 0.02 to2.0 weight percent, each of said weight percentages being the percentageof the total weight of said ceramic composition.

2. A piezoelectric ceramic composition according to claim 1, wherein theset of said additional constituents consists of a manganous oxide offrom `0.02 to 1.0 weight percent and a nickel oxide of from 0.02 to 2.0weight percent, each of the weight percentages being the percentage ofthe total weight of said ceramic composition.

3. A claim according to claim 1, in Which the piezoelectric compositionhas been subjected to a polarization treatment at temperatures of 50 to150 degrees centigrade.

4. A piezoelectric ceramic composition having the following formula andPb (ZrXTiySnz) O3 where x, y and z are given by x=0.00-0.90 y=0.10-0.60z=0.000.65

and

References Cited UNITED STATES PATENTS 2,928,163 3/196-0 Berlincourt etal. 252-62.9 X 3,068,177 12/1962 Sugden 252-629 3,372,121 3/1968 Banno252--62.9

HELEN M. MCCARTHY, Primary Examiner I. COOPER, Assistant Examiner U.S.Cl. X.R. 106-39

